Versatile Coordination of a Reactive P, N-Ligand Toward Boron, Aluminum

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Versatile coordination of a reactive P,N-ligand toward boron, aluminum and gallium and Cite this: Dalton Trans., 2016, 45, 10989 interconversion reactivity†

M. Devillard,a C. Alvarez Lamsfus,b V. Vreeken,a L. Maronb and J. I. van der Vlugt*a

The synthesis and reactivity of the ﬁrst Group 13 complexes bearing a dearomatized phosphino-amido

ligand L are reported, i.e. alane AlEt2(L) 1, gallane GaCl2(L) 2 and borane B(Cl)(Ph)(L) 3. The three com-

Received 24th May 2016, plexes react very diﬀerently with Group 13 trihalogenides, providing access to zwitterionic anti-3·GaCl3 Accepted 9th June 2016 and the unique bis(metalloid) 5·BCl2, with the boron center part of a highly unusual anionic four-mem- DOI: 10.1039/c6dt02087a bered ring (charge on C) and Ga bound to P. The coordination chemistry and the various transformations www.rsc.org/dalton are supported by DFT calculations, X-ray crystallography and multinuclear NMR spectroscopic data.

Creative Commons Attribution-NonCommercial 3.0 Unported Licence. Introduction tivity of complexes bearing a dearomatized P,N ligand is currently unknown but it could be envisioned that other ligand coordi- The synthetic chemistry and reactivity of Group 13 complexes nation modes may be accessible with these elements. has recently attracted much attention, both with respect to the To address both challenges, we decided to exploit the preparation of unsaturated derivatives1 and for application in reversible dearomatization chemistry of P,N-ligands to generate bond activation processes and homogeneous catalysis,2 often the first examples of Group 13 species with a dearomatized in combination with a Lewis base as a “Frustrated Lewis Pair” pyridine ligand (see Scheme 1). This approach has allowed (FLP).3 At the same time, the bioinspired strategy to combine access to highly reactive aluminum, gallium and boron ‘ ’ ff This article is licensed under a proton-responsive ( reactive ) ligands and (transition) metal compounds stabilized by an anionic P,N-sca old and to study centers has become prominent, resulting in novel coordi- their versatile reactivity with G13 trihalogenides. nation chemistry with applications in small molecule activation and metal–ligand bifunctional catalysis.4 Open Access Article. Published on 09 June 2016. Downloaded 1/31/2020 3:03:39 AM. One particular strategy that has come to the forefront in this context is the use of lutidine- and picoline-based P,N donor Results and discussion ligands that can undergo reversible dearomatization.5 Many Reaction of the known bidentate P,N-ligand 2-(diphenylphos- transition metals coordinate strongly to both phosphorus and phinomethyl)-6-methyl-pyridine LH with one molar equivalent nitrogen in these ligands,6 and deprotonation of the ligand back- of n-BuLi followed by electrophilic trapping with chlorodiethyl- bone merely generates a nucleophilic carbon center that does not aluminum (Scheme 2) resulted in the high yield synthesis of engage in any direct interaction with the metal coordination complex AlEt (L) 1 as a red oil, which was characterized by sphere.Noexamplesoftransmetallationoncomplexesbearing 2 multinuclear NMR spectroscopy. Contrary to what was pre- lutidine- or picoline-derived P,N-ligands are known, to the best of viously observed for the anion of lutidine,8 this reaction selec- our knowledge.7 The coordination chemistry of Group 13 metals tively generates an N-Group 13 element bond, with and metalloids such as boron and aluminum is unexplored with dearomatization of the N-heterocycle, rather than a C-Group this type of reactive ligand scaffold. Hence, the fundamental reac- 13 bond. The 1H NMR spectrum contained three different resonances in the olefinic region (δ 5.28, 6.07 and 6.42) and a δ a ’ ff broad signal at 3.46 attributed to the methine proton of the Homogeneous, Bioinspired and Supramolecular, van tHo Institute for Molecular v – Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, CH PPh2 arm. Only one resonance was observed for the two The Netherlands. E-mail: [email protected] tert-butyl groups connected to phosphorus and both Et-groups b Laboratoire de Physique et Chimie des Nanoobjets, Université de Toulouse, at aluminum are also equivalent, confirming the Cs symmetry INSA-UPS-CNRS (UMR 5215) 135, avenue de Rangueil, 31077 Toulouse cedex 4, of the molecule. This compound features a clear P → Al inter- France action, as evidenced by the broad 31P NMR signal at δ −0.9 (Δδ †Electronic supplementary information (ESI) available. CCDC 1455266–1455269, − H 27 δ 1481714. For ESI and crystallographic data in CIF or other electronic format see 36.2 relative to L ) and the Al NMR resonance at 162, 9 DOI: 10.1039/c6dt02087a which is characteristic of a four-coordinated amido-alane.

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Scheme 1 Dearomatized Group 13 complexes of (phosphinomethyl)pyridine ligands described in this work, their reactivity with Group 13 trihalogenides and follow-up transformations.

The ligand framework adopts an almost planar configuration, with the phosphine and alane fragments slightly out of the ∠ – – – ∠ – – – Creative Commons Attribution-NonCommercial 3.0 Unported Licence. N-heterocycle plane ( P2 C4 C6 C7 177.8°, Al1 N1 C6 C7 174.6°). The N-heterocycle shows clear alternation of C–C and CvC bonds. The HOMO is mainly located on the C1 carbon Scheme 2 Preparation of the phosphorus-stabilized amidoalane 1 and (64.1%), suggesting that this alane complex with an anionic subsequent transmetallation to form the parent gallane 2. P,N ligand would likely react with electrophiles at the methine

site, as previously established for e.g. MeOTf, CO2 and nitrile electrophiles with either Cu and Ru complexes bearing dearo- H Strikingly, the analogous reaction of L with AlCl3 failed to matized P,N pincers.10 However, common inorganic Lewis generate any well-defined product. acids have not been employed as electrophiles, to the best of This article is licensed under a To get insight into the geometric and electronic features of our knowledge. 1, we optimized its structure using DFT calculations (Fig. 1). We thus explored its reactivity toward gallium trichloride as

a prototypical Lewis acid (Scheme 2). After addition of GaCl3 to

Open Access Article. Published on 09 June 2016. Downloaded 1/31/2020 3:03:39 AM. a solution of 1 in toluene at room temperature and work-up, the 31P NMR spectrum contained only a very broad resonance at δ −3.1, while the 1H NMR spectrum still showed the characteristic pattern for a dearomatized P,N backbone, but was

lacking any signals for an AlEt2 fragment. These spectroscopic data indicate a formal transmetallation from Al to Ga to gen- + erate GaCl2(L) 2, which was detected by HR-MS data (FD , m/z = 390.04338), and AlClEt2. The structure of this gallane complex 2 was confirmed by X-ray structure determination on air-sensi-

tive orange crystals of GaCl2(L), obtained from a diethyl ether- toluene solution at r.t. (Fig. 2). In the crystal structure, the geometry around gallium is strongly pyramidal due to the interaction with the phosphine donor (sum of angles 331.9°). The N-heterocycle shows alternation of single and double C–C bonds, while the external C–C double bond lies in-between (C1–C2 = 1.394(2) Å) and the C1 carbon is clearly sp2 hybridized. The intriguing conversion of 1 into 2 may be envisioned to involve initial formation of a bis-metalloid intermediate

1·GaCl3 with a C–Ga bond and a formally cationic Al-center, Fig. 1 (Top) HOMO and (bottom) LUMO frontier orbital plots (top and but this proposed intermediate could not be detected using 1, side views) for the phosphorus-stabilized amidoalane 1. despite various attempts. We hypothesized that such a bis-

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Fig. 2 Displacement ellipsoid plot (50% probability level) of 2. Hydro- Fig. 3 Displacement ellipsoid plot (50% probability level) of anti-

gen atoms (except for hydrogen on C1) are omitted for clarity. Selected 3·GaCl3. Hydrogen atoms (apart from those on C1) are omitted for bond lengths (Å) and angles (°): P1–Ga1 2.339(1); N1–Ga1 1.946(1); Ga1– clarity. Selected bond lengths (Å) and angles (°): P1–C1 1.830(2); C1–C2 Cl1 2.185(1); P1–C1 1.743(2); C1–C2 1.394(2); C2–C3 1.433(2); C3–C4 1.501(3); P1–B1 2.021(2); N1–B1 1.602(3); B1–Cl1 1.869(2); B1–C8 1.354(2); C4–C5 1.412(3); C5–C6 1.360(2); P1–Ga1–N1 90.0(1); P1– 1.596(3); C1–Ga1 2.030(2); P1–B1–N1 98.0(1); P1–C1–Ga1 126.4(1); Ga1–Cl1 116.6(1); P1–C1–C2 120.8(1); P1–C1–C2–N1–1.3. N1–B1–Cl1 111.3(1); N1–B1–C8 110.1(2); P1–C1–C2–N1 22.5.

Creative Commons Attribution-NonCommercial 3.0 Unported Licence. metalloid structure could be more readily accessible with B zwitterionic anti-3·GaCl3 (anti refers to the relative positions of instead of Al, as boron cations are known to be stable in tetra- the chloride at boron and the GaCl3 fragment with respect to coordinated environments (commonly termed boroniums).11 the G13-pyridine plane, Fig. 3). The new C1–Ga1 bond is in the The boron analogue of 1 could be accessed via deprotonation range of previously reported carbogallates.12 The boronium H of L and subsequent addition of Cl2BPh (Scheme 3). Complex fragment is strongly pyramidalized (sum of angles 333.5°). B(Cl)(Ph)(L) 3 was obtained in 53% yield as a very air-sensitive DFT calculations (Gaussian 09, B3PW91, 6-31G**) show that −1 red oil that was completely characterized by multinuclear NMR the syn-3·GaCl3 diastereoisomer is 3.7 kcal mol higher in and HR-MS (CSI [M + H]+, m/z 374.1976). The 31P NMR spec- energy, which is within the upper limit of the precision of the trum of 3 shows a broad resonance at δ 24.5 (Δδ = −10.8 ppm) methods. Heating a solution of anti-3·GaCl3 for 10 h at 100 °C

This article is licensed under a 11 and the doublet in B NMR is found in the typical region for led to partial isomerization to syn-3·GaCl3, as evidenced by 1 tetracoordinated boron atoms (δ 5.1, JBP = 106 Hz), confirming multinuclear NMR spectroscopy. its connectivity to phosphorus. The 1H NMR spectrum of 3 Although there is some precedent for nucleophilic attack of 2 Open Access Article. Published on 09 June 2016. Downloaded 1/31/2020 3:03:39 AM. δ showed a doublet at 3.46 ( JHP = 5.1 Hz) attributed to the dearomatized pincer transition metal complexes on a Group 13 proton of the vCH–PPh2 arm. 13 Lewis acid, this reactivity is unprecedented for main

Addition of 1 eq. of GaCl3 to 3 instantaneously yielded a group elements or metalloids. Moreover, given the propensity yellow precipitate, which was characterized by a broad signal of GaCl3 to act as halide scavenger toward main group halides, at δ 34.0 in the 31P NMR spectrum (Δδ = 9.5 ppm) and a including boron for the generation of boron cations,14 the slightly upfield shifted 11B NMR signal (δ 5.6); (Δδ = 0.5 ppm). observed preference to act as electrophile in a carbon–gallium The presence of a doublet at δ 3.67 in the 1H NMR spectrum bond formation step is deemed highly remarkable. This bond 2 with a relatively large JHP coupling constant of 13.4 Hz (ΔJ = is indeed reactive, as evidenced by the reaction of anti-3·GaCl3 8.3 Hz compared to 3) indicates rearomatization of the N-het- with HCl, which led to protonation at the methylene carbon

erocycle and supports addition of GaCl3 to the methylene with the formation of tetrachlorogallate salt 4 (Scheme 4), carbon spacer. Single crystal X-ray structure determination which was fully characterized, including by single crystal X-ray confirmed the diastereoselective formation of the formally structure determination (Fig. 4).

Scheme 3 Preparation of the phosphorus-stabilized amidoborane 3

and its reaction with GaCl3 to form the zwitterion anti-3·GaCl3. Scheme 4 Reaction of anti-3·GaCl3 with HCl to give 4.

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Fig. 5 Displacement ellipsoid plot (50% probability level) of 5·BCl2. Hydrogen atoms (apart from those on C1) are omitted for clarity. Selected bond lengths (Å) and angles (°): P1–C1 1.832(2); C1–C2 1.516(4); Fig. 4 Displacement ellipsoid plot (50% probability level) of 4. Hydro- N1–C2 1.352(3); N1–B1 1.586(3); C1–B1 1.682(3); B1–Cl1 1.819(2); gen atoms are omitted for clarity. Selected bond lengths (Å) and angles P1–Ga1 2.389(1); Ga1–Cl3 2.179(1); P1–C1–B1 132.2(2) (1); C2–C1–B1 – – – – (°): P1 B1 2.018(2); N1 B1 1.608(2); B1 Cl1 1.859(2); B1 C16 1.597(3); 84.4(2); C1–B1–N1 83.3(2); B1–N1–C2 93.9(2); N1–C2–C1 98.4(2); P1– – – – – – – P1 C1 1.817(2); C1 C2 1.502(2); P1 B1 N1 97.4(1); P1 B1 N1 109.3(1); C1–C2–N1–136.0. P1–B1–C16 113.7(1); P1–C1–C2 105.4(1); P1–C1–C2–N1–27.3.

The electronegativity of Ga lies in-between that of B and Al. methine spacer of a dearomatized lutidinylphosphine engages We decided to explore the reaction of gallane 2 with boron tri- in direct coordination to a metal(loid). The only two structu-

Creative Commons Attribution-NonCommercial 3.0 Unported Licence. chloride as Lewis acid in order to probe whether the resulting rally characterized fused heterobicyclic structures with boron reactivity of these Group 13 elements bound to a dearomatized and pyridine resulted either from (i) C–H activation of a luti- – P,N ligand follows the same trend. Upon addition of BCl3 to 2, dine borenium adduct in the presence of an external Lewis the bright orange reaction mixture turned colorless, which is base15 or (ii) ring-closure of a bis(pentafluorophenyl)boryl diagnostic of re-aromatization (Scheme 5). derived FLP.16 In both cases, extremely strong Lewis acids are The broad 31P NMR signal appeared at lower field (δ involved. 31.1 ppm, Δδ −10.8 ppm) with no evidence for P–B coupling, Given its unique nature, we decided to get further insight indicative that the phosphine is still connected to gallium. In into the bonding situation within 5·BCl2 by DFT calculations. 1 v – δ – the H NMR spectrum, the CH PPh2 proton is deshielded ( Natural bond order (NBO) analysis demonstrated that the C1 This article is licensed under a 3.93 ppm) and broadened due to scalar proximity of a 11B B1 and the N1–B1 bonds are very polarized toward C and N nucleus (confirmed by 1H{11B} NMR analysis). Single crystal (70% and 80%, respectively). In line with this observation, the

X-ray structure determination of 5·BCl2 confirmed the incor- Natural Population Analysis (NPA) showed a positively charged

Open Access Article. Published on 09 June 2016. Downloaded 1/31/2020 3:03:39 AM. poration of both Ga and B (Fig. 5). However, concomitant with boron atom (+0.4). Interestingly, the C1 carbon atom bears a − exchange of Ga for B for the coordination to the heterocycle significant negative charge ( 0.9). As a result, 5·BCl2 is best nitrogen atom, the latter has undergone an unprecedented described as the combination of a boronium and an anionic change from a P,N to a C,N binding pocket. C,N ligand. The carbanion might be partially stabilized by The boron atom is incorporated in a rare four-membered negative hyperconjugation into the σ*(P–C) orbitals as in ring that is fused to a rearomatized pyridine ring ( judging reported α-monolithiated17 and α-dilithiated18 phosphine- from the almost identical carbon–carbon bond lengths in the boranes, although second order NBO analysis does not provide ring). The carbon atom binds to boron while the pendant clear evidence for this. The analogous 5·B(Cl)(Ph) was phosphine binds the trichlorogallane. The C1–B1 bond length obtained as a mixture of diastereomers by reacting 2 with of 1.682(3) Å likely reflects the ring-strain in this structure. To BCl2Ph. the best of our knowledge, this is the first example wherein the Compounds 3·GaCl3 and 5·B(Cl)(Ph) are linkage isomers (Scheme 6). The average DFT calculated energy diﬀerences of

the linkage isomers 3·GaCl3 and 5·B(Cl)(Ph) (syn and anti)are within the upper limit of the precision of the methods − (3.6 kcal mol 1 in favor of 5·B(Cl)(Ph)). Given this small energy diﬀerence, we speculated that 5·B(Cl)(Ph) could conceivably still be of relevance in the formal transmetallation of 2 with

BCl2Ph to provide 3·GaCl3 under forcing conditions. To verify

this hypothesis, a solution of 5·B(Cl)(Ph) in CD2Cl2 was heated in a pressure tube to 100 °C for 6 hours, which cleanly gener-

Scheme 5 Preparation of 5·BCl2 and 5·B(Cl)(Ph) by reaction of 2 with ated 3·GaCl3 as a mixture of diastereoisomers. It is plausible haloboranes. that this structural rearrangement, involving both C–B and

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Scheme 6 Thermal linkage isomerization of 5·B(Cl)(Ph) into 3·GaCl3, proposedly with intermediacy of 3 and free GaCl3. Fig. 6 Displacement ellipsoid plot (50% probability level) of 6. Hydro- gen atoms (apart from those on C1) are omitted for clarity. Selected bond lengths (Å) and angles (°): N1–B1 1.5805(25); B1–C1 1.6841(26); – – – – P–Ga bond cleavage and C–Ga as well as P–B bond formation, P1 B2 2.0441(21); C1 C2 1.5188(25); B1 Cl1 1.8220(21); B1 Cl2 1.8481(22); P1–C1 1.8419(19); N1–B1–C1 83.64(12); P1–C1–B1 133.05(13); proceeds via reconstitution of a mixture of 3 (with the de- N1–B1–Cl1 113.40(13); C1–P1–B2 105.87(8); P1–C1–C2–N1–135.23. aromatized N-heterocycle) and GaCl3, which were found to react instantaneously at room temperature. With the well-defined coordination chemistry for the 13 halogenides is observed. The rich coordination chemistry of heterodinuclear species in hand, we wondered if the reaction this reactive ligand scaﬀold with G13 elements may open up of 1 with boron trichloride would also lead to selective trans- e.g. new avenues for non-transition metal based small mole- Creative Commons Attribution-NonCommercial 3.0 Unported Licence. metallation and generation of product BCl (L) (as observed 2 cule activation and cooperative catalysis. Research in this with GaCl ) or an analogous reaction as observed for 3 to 5 but 3 direction is currently ongoing in our laboratories. with a phosphino-alane pendant arm. The addition of one

equivalent of BCl3 to a solution of alane 1 at room temperature led to only 50% conversion of starting material, but the reaction smoothly went to completion when two equivalents of Experimental section BCl were used (Scheme 7). 3 General comments The new species gives rise to a quadruplet in 31P NMR at δ 22.8, which is characteristic of the direct coordination of the All reactions and manipulations were carried out under an This article is licensed under a phosphine to a boron atom. In line with the required stoichio- atmosphere of dry dinitrogen using standard Schlenk tech- metry, the 11B NMR shows two signals, a doublet at δ 4.7 with niques or in a glove-box. All solvents were purged with dinitro- 1 a JBP = 139.4 Hz and a broad singlet at δ 6.6. Single crystal gen and dried using an MBRAUN Solvent Purification System 1 13 31 11 27 Open Access Article. Published on 09 June 2016. Downloaded 1/31/2020 3:03:39 AM. X-ray structure determination of 6 confirmed the incorporation (SPS). H, C, P, B and Al NMR spectra were recorded on of two boron atoms in the molecule (Fig. 6). Complex 6 is Bruker AV 300, Bruker DRX 300 or Bruker AV 400 spec-

structurally related to borane–gallane 5.BCl2, with the same trometers. Chemical shifts were expressed in positive sign, in 1 13 strained four-membered ring including the boron atom, but parts per million, calibrated to residual H (5.32 ppm) and C featuring a trichloroborane-coordinated phosphine arm. It is (53.84 ppm) solvent signals, external BF3·Et2O, 85% H3PO4

likely that the interaction of AlClEt2 with the pendant phos- and Al(NO3)3 1 M in D2O (0 ppm) respectively. Mass spectra phine is relatively weak (perhaps partly due to steric hindrance), were recorded on an AccuTOF LC, JMS-T100LP or an AccuTOF resulting in facile displacement by an additional equivalent GC v 4 g, JMS-T100GCV Mass spectrometer. Di-(tert-butylphos- H of BCl3. phino)methyl-6-methyl-pyridine L was prepared according to 19 In summary, we demonstrate the first examples of Group 13 a literature procedure. complexes (boron, gallium and aluminum) stabilized by a Complex 1. A solution of nBuLi (2.5 M in hexanes, 0.25 mL, dearomatized P,N ligand. Depending on the nature of the 0.63 mmol, 1 eq.) was added dropwise to an ice-cooled stirred metal(loid) involved, very diﬀerent reactivity toward Group solution of 2-(di-tert-butylphosphino)methyl-6-methyl-pyridine LH (157 mg, 0.63 mmol) in diethylether (6.5 mL) and the resulting orange solution was allowed to react for 1 h at the same temperature. Then, the reaction mixture was cooled down to −78 °C and chlorodiethylaluminum (0.32 M in toluene, 1.98 mL, 1.01 eq.) was added dropwise. The reaction mixture was allowed to warm up to room temperature over 1 h, giving an orange solution and a white precipitate. After elimination of the salts by filtration and removal of the volatiles under reduced

Scheme 7 Synthesis of 6 by transmetallation of 1 with 2 equiv. BCl3. pressure, 1 wasobtainedasaredoilin95%yield.

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1 H NMR (300 MHz, CD2Cl2, δ): 0.18 (m, 4H, CH2Et), 1.05 (t, dried aﬀording the expected compound in a mixture with the 3 3 6H, JHH = 8.0 Hz, CH3Et), 1.25 (d, 18H, JHP = 13.9 Hz, tBu), starting material (7.7/1) (yield = 53%) due to partial hydrolysis. 1 3 2.06 (s, 3H, CH3Me), 3.46 (s br., 1H, CvC(H)(P̲ tBu2)), 5.28 (d, H NMR (300 MHz, CD2Cl2, δ): 0.95 (d, 9H, JHP = 13.7 Hz, 3 3 3 1H, JHH = 6.5 Hz, Csp2–H), 6.07 (d, 1H, JHH = 9.1 Hz, Csp2–H), tBu), 1.51 (d, 9H, JHP = 13.3 Hz, tBu), 1.92 (s, 3H, CH3), 3.46 3 3 5 – 2 v ̲ 3 6.42 (ddd, 1H, JHH = 9.1 Hz, JHH = 6.5 Hz, JHP = 1.5 Hz, Csp2 (d, 1H, JHP = 5.1 Hz, C C(H)(PtBu2)), 5.40 (d, 1H, JHH = 6.5 31 1 27 1 3 H). P{H} NMR (121 MHz, CD2Cl2, δ): −0.9 (br.). Al { H} Hz, Csp2–H), 6.25 (d, 1H, JHH = 8.9 Hz, Csp2–H), 6.59 (ddd, 1H, 13 1 3 3 5 NMR (78 MHz, CD2Cl2, δ): 162 (br.) C{H} NMR (75 MHz, JHH = 8.9 Hz, JHH = 6.5 Hz, JHP = 1.4 Hz, Csp2–H), 7.10–7.24 δ – 3 – CD2Cl2, ): 2.5 (br., 2C, CH2Et), 9.5 (s, 2C, CH3Et), 23.1 (s, 1C, (m, 3H, Csp2 H), 7.33 (t, 1H, JHH = 7.4 Hz, Csp2 H), 7.91 (d, 2 1 3 11 1 CH3), 29.3 (d, 6C, JCP = 4.8 Hz, CH3tBu), 34.3 (d, 2C, JCP = 23.5 1H, JHH = 7.4 Hz, Csp2–H). B{H} NMR (96 MHz, CD2Cl2, δ): 1 1 31 1 Hz, P–CtBu), 57.4 (d, 1C, JCP = 50.5 Hz, P–Csp2), 102.7 (s, 1C, 5.1 (d, JBP = 106.0 Hz). P{H} NMR (121 MHz, CD2Cl2, δ): – – 13 1 δ Csp2 H), 118.1 (d, 1C, JCP = 12.4 Hz, Csp2 H), 133.9 (d, 1C, JCP = 24.5 (s br.). C{H} NMR (75 MHz, CD2Cl2, ): 22.6 (s, 1C, 1 2.5 Hz, Csp2–H), 150.9 (d, 1C, JCP = 4.4 Hz, Cquat.), 167.2 (d, 1C, CH3), 28.7 (s, 3C, CH3tBu), 29.4 (s, 3C, CH3tBu), 34.7 (d, 1C, JCP 1 JCP = 14.9 Hz, Cquat.). The highly air-sensitive nature of this oil = 24.4 Hz, P–CtBu), 38.8 (d, 1C, JCP = 23.1 Hz, P–CtBu), 53.0 (d, 1 – – (slow decomposition even in an N2-filled glovebox) interfered 1C, JCP = 65.2 Hz, P Csp2), 106.0 (d, 1C, JCP = 1.7 Hz, Csp2 H), during our repetitive attempts to obtain high-resolution mass 116.2 (d, 1C, JCP = 14.3 Hz, Csp2–H), 127.2 (d, 1C, JCP = 1.2 Hz,

analysis and elemental analysis. Csp2–H), 127.3 (d, 1C, JCP = 2.3 Hz, Csp2–H), 127.8 (d, 1C, JCP = – – Complex 2. Gallium trichloride (350.3 mg, 1.99 mmol, 1 eq.) 1.6 Hz, Csp2 H), 133.4 (d, 1C, JCP = 2.9 Hz, Csp2 H), 135.0 (d, in toluene (5 mL) was added dropwise to an in situ prepared 1C, JCP = 2.1 Hz, Csp2–H), 136.0 (d, 1C, JCP = 2.3 Hz, Csp2–H),

solution of 1 (667.3 mg, 1.99 mmol) in diethyl ether (25 mL) 151.3 (d, 1C, JCP = 9.1 Hz, Cquat.), 167.6 (d, 1C, JCP = 13.8 Hz,

under stirring at room temperature and the resulting mixture Cquat.), the aromatic carbon connected to boron is not was stirred for an additional 4.5 h. Then, volatiles were observed. HRMS (CSI, −30 °C): exact mass (monoisotopic) + removed under vacuum leading to an orange residue. This calcd for [C21H30BClNP + H] , 374.1976; found 374.1980. This

Creative Commons Attribution-NonCommercial 3.0 Unported Licence. residue was extracted with a mixture of dichloromethane/ compound proved too hydrolysis-sensitive for satisfactory com- pentane (0.3 mL/10 mL) and filtered. The resulting solution bustion analysis data.

was concentrated to 2 mL, resulting in the crystallization of 2 Complex anti-3·GaCl3. A solution of 3 (445 mg, 1.19 mmol) at room temperature as sticky orange blocks in 96% yield. in ether (15 mL) was added slowly to a solution of gallium tri- Crystals suitable for X-ray crystallography were obtained from a chloride (210 mg, 1.19 mmol, 1 eq.) in toluene (4 mL) at saturated solution of 2 in a toluene/diethylether mixture at r. t. under stirring. The reaction mixture was then further 1 δ room temperature. H NMR (300 MHz, CD2Cl2, ): 1.40 (d, stirred for 30 minutes leading to an orange solution and a 3 2 18H, JHP = 16.1 Hz, tBu), 2.35 (s, 3H, CH3), 3.46 (d, 1H, JHP = yellowish precipitate. After removal of the mother liquor via

3.3 Hz, CvC(H)(P̲ tBu2)), 5.53 (d, 1H, JHH = 6.6 Hz, Csp2–H), cannula filtration, the precipitate was extracted with dichloro- This article is licensed under a – 6.24 (d, 1H, JHH = 9.0 Hz, Csp2 H), 6.62 (ddd, 1H, JHH = 9.0 Hz, methane (20 mL), filtered and the limpid dichloromethane 31 1 JHH = 6.6 Hz, JHP = 1.3 Hz, Csp2–H). P{H} NMR (121 MHz, solution thus obtained was layered with pentane (21 mL), 13 1 CD2Cl2, δ): −3.1 (br.). C{H} NMR (75 MHz, CD2Cl2, δ): 22.7 aﬀording colorless crystals of anti-3·GaCl3 in a yield of 40%. 2 1 Open Access Article. Published on 09 June 2016. Downloaded 1/31/2020 3:03:39 AM. ﬀ (s, 1C, CH3), 28.9 (d, 6C, JCP = 2.8 Hz, CH3tBu), 36.8 (d, 2C, JCP Crystals suitable for X-ray di raction analysis were obtained 1 1 = 30.4 Hz, P–CtBu), 50.7 (d, 1C, JCP = 67.6 Hz, P–Csp2), 105.5 (d, under the same conditions. H NMR (300 MHz, CD2Cl2, δ): 3 3 1C, JCP = 1.2 Hz, Csp2–H), 119.2 (d, 1C, JCP = 12.0 Hz, Csp2–H), 1.31 (d, 9H, JHP = 15.8 Hz, tBu), 1.50 (d, 9H, JHP = 13.6 Hz, – 2 – ̲– 135.7 (d, 1C, JCP = 2.3 Hz, Csp2 H), 151.2 (d, 1C, JCP = 4.3 Hz, tBu), 2.42 (s, 3H, CH3), 3.67 (d, 1H, JHP = 13.4 Hz, P C(H) Ga), Cquat.), 166.7 (d, 1C, JCP = 6.7 Hz, Cquat.). HRMS (FD): exact 7.04 (m, 1H, Harom.), 7.18 (m, 1H, Harom.), 7.29 (m, 1H, Harom.), 69 35 + mass (monoisotopic) calcd for [C15H25 GaNP Cl2 +H], 7.34 (m, 1H, Harom.), 7.43 (m, 1H, Harom.), 7.96–8.05 (m, 2H, 3 31 1 390.04357; found 390.04338. Despite several attempts, no satis- Harom.), 8.51 (d, 1H, JHH = 8.2 Hz, Harom.). P{H} NMR 11 1 factory combustion analysis data was obtained for this com- (121 MHz, CD2Cl2, δ): 34.0 (br.). B{H} NMR (96 MHz, 13 1 pound, likely as a result of its air-sensitive nature. CD2Cl2, δ): 5.6. C{H} NMR (75 MHz, CD2Cl2, δ): 23.4 (s, 1C, – Complex 3. A solution of nBuLi (2.5 M in hexanes, 0.21 mL, CH3), 28.8 (s, 3C, CH3tBu), 30.0(s, 3C, CH3tBu), 32.6 (br., P 1 1 0.52 mmol, 1 eq.) was added dropwise under stirring to an ice- C(H)̲ –Ga), 36.6 (d, 1C, JCP = 24.4 Hz, P–CtBu), 39.6 (d, 1C, JCP

cooled solution of 2-(di-tert-butylphosphino)methyl-6-methyl- = 23.1 Hz, P–CtBu), 123.5 (d, 1C, JCP = 9.2 Hz, CHarom.), 127.1

pyridine (150 mg, 0.52 mmol) in diethylether (5 mL) and the (d, 1C, JCP = 1.9 Hz, CHarom.), 128.4 (s, 2C, CHarom.), 129.2 (d, resulting orange solution was allowed to react for 1 h at the 1C, JCP = 2.3 Hz, CHarom.), 134.7 (d, 1C, JCP = 2.2 Hz, CHarom.),

same temperature. Then, the reaction mixture was cooled 135.1 (d, 1C, JCP = 2.9 Hz, CHarom.), 143.0 (d, 1C, JCP = 1.7 Hz, − μ down to 78 °C and dichlorophenylborane (77 L, 0.52 mmol, CHarom.), 157.9 (d, 1C, JCP = 7.4 Hz, Cquat.), 164.5 (d, 1C, JCP = 1 eq.) was added dropwise. The reaction mixture was allowed 3.7 Hz, Cquat.), the aromatic carbon connected to boron is not

to warm up to room temperature over 30 minutes and was observed. Anal. Calcd For C21H30BCl4GaNP; C, 45.88; H, 5.50; further stirred for 1 h at room temperature, giving an orange N, 2.55. Found: C, 45.81; H, 5.43; N, 2.49. M. p.: decompo- solution and a white precipitate. Only 3 was detected in the sition above 200 °C. 31 1 crude mixture by P{ H} NMR analysis. After removal of the Isomerization of anti-3·GaCl3. A solution of anti-3·GaCl3 μ volatiles, the residue was extracted with pentane (3 mL) and (14.6 mg, 26.6 mol) in CD2Cl2 (0.4 mL) was heated at 100 °C

10994 | Dalton Trans.,2016,45,10989–10998 This journal is © The Royal Society of Chemistry 2016 View Article Online

Dalton Transactions Paper

1 for 10 h, leading to partial isomerization to its diastereoisomer CD2Cl2, δ): 23.6 (s, 1C, CH3), 23.7 (d, 1C, JCP = 27.8 Hz, CH2), 1 syn-3·GaCl3 in a 0.70/1.0 (anti/syn) ratio (as determined by inte- 28.8 (s, 3C, CH3tBu), 29.1 (s, 3C, CH3tBu), 35.2 (d, 1C, JCP = 18.6 1 1 gration of each vCHPPh2 signal in the H NMR spectrum, D1 Hz, P–CtBu), 37.3 (d, 1C, JCP = 21.1 Hz, P–CtBu), 125.0 (d, 1C,

= 10 s). The mixture of diastereoisomers was fully character- JCP = 7.5 Hz, CHarom.), 129.0 (d, 1C, JCP = 2.3 Hz, CHarom.),

ized by NMR spectroscopy: anti-3·GaCl3 =A;syn-3·GaCl3 = 129.5 (d, 1C, JCP = 2.3 Hz, CHarom.), 130.0 (d, 1C, JCP = 3.0 Hz, 1 3 B. H NMR (400 MHz, CD2Cl2, δ): 1.29 (d, 9H, JHP = 15.2 Hz, CHarom.), 130.5 (d, 1C, JCP = 2.3 Hz, CHarom.), 131.5 (d, 1C, JCP = 3 3 tBu(B)), 1.31 (d, 9H, JHP = 15.5 Hz, tBu(A)), 1.50 (d, 9H, JHP = 2.3 Hz, CHarom.), 135.2 (d, 1C, JCP = 3.0 Hz, CHarom.), 145.3 (d, 3 13.3 Hz, tBu(A)), 1.53 (d, 9H, JHP = 12.7 Hz, tBu(B)), 2.42 (s, 1C, JCP = 0.8 Hz, CHarom.), 156.0 (d, 1C, JCP = 3.0 Hz, Cquat.), 2 3H, CH3(A)), 2.53 (s, 3H, CH3(B)), 3.27 (d, 1H, JHP = 13.6 Hz, 159.7 (d, 1C, JCP = 6.8 Hz, Cquat.) the aromatic carbon con- 2 P–C(H)̲–Ga (B)), 3.68 (d, 1H, JHP = 13.5 Hz, P–C(H)̲–Ga (A)), nected to boron is not observed. Anal. Calcd For 3 6.44 (d, 1H, JHH = 7.7 Hz, Harom.(B)), 7.04 (m, 1H, Harom.(A)), C21H31BCl5GaNP; C, 43.03; H, 5.33; N, 2.39. Found: C, 42.87; 7.14–7.21 (m, 1Harom.(A) + 1Harom.(B)), 7.26–7.37 (m, 2Harom.(A) H, 5.20; N, 2.38. M. p.: 205–209 °C.

+1Harom.(B)), 7.95–8.04 (m, 1Harom.(A) + 1Harom.(B)), 8.07 (d Complex 5·BCl2. Boron trichloride in toluene (1 M, 0.65 mL, 3 3 br., 1H, JHH = 7.4 Hz, Harom.(B)), 8.13 (t, 1H, JHH = 8.0 Hz, 0.65 mmol, 1 eq.) was added dropwise at room temperature to 3 Harom.(B)), 8.51 (d, 1H, JHH = 8.5 Hz, Harom.(A)), 8.60 (d, 1H, a solution of 2 (255 mg, 0.65 mmol) in toluene (5 mL) under 3 31 1 JHH = 8.1 Hz, Harom.(B)). P{H} NMR (162 MHz, CD2Cl2, δ): stirring. Upon addition, the solution changed from orange to 11 1 δ 34.1 (br., A), 43.4 (br., B). B{H} NMR (128 MHz, CD2Cl2, ): colorless. Then, pentane (20 mL) was added and the reaction 13 1 5.3 (br.). C{H} NMR (101 MHz, CD2Cl2, δ): 23.4 (s, 1C, mixture was slowly concentrated until a white powder precipi-

CH3(A)), 24.4 (s, 1C, CH3(B)), 28.1 (br., 1C, P–C(H)̲ –Ga(B)), 28.8 tated. After removal of the supernatant via cannula filtration,

(s, 1C, CH3tBu(A)), 29.3 (s, 2C, CH3tBu(B)), 30.0 (s, 1C, the solid material was dried under reduced pressure. The solid 1 CH3tBu(A)), 32.6 (br., 1C, P–C(H)̲ –Ga(A)), 35.2 (d, 1C, JCP = 23.7 was then dissolved in dichloromethane (3 mL) and filtered 1 Hz, P–CtBu(B)), 36.6 (d, 1C, JCP = 24.5 Hz, P–CtBu(A)), 38.3 (d, again. Layering of this solution with pentane (8 mL) led to the 1 – 1 – Creative Commons Attribution-NonCommercial 3.0 Unported Licence. 1C, JCP = 22.2 Hz, P CtBu(B)), 39.5 (d, 1C, JCP = 23.0 Hz, P crystallization of 5·BCl2 at room temperature in 3 days as color- CtBu(A)), 123.5 (d, 1C, JCP = 9.1 Hz, CHarom.(A)), 126.2 (d, 1C, less crystals with a yield of 34%. Crystals suitable for X-ray

JCP = 7.8 Hz, CHarom.(B)), 127.1 (d, 1C, JCP = 1.9 Hz, diﬀraction analysis were obtained by slow diﬀusion of pentane

CHarom.(A)), 128.4 (br., 2C, CHarom.(A)), 128.7 (br, 1C, into a saturated dichloromethane solution of 5·BCl2 at room 1 3 CHarom.(B)), 128.9 (d, 1C, JCP = 2.4 Hz, CHarom.(B)), 129.0 (br, temperature. H NMR (300 MHz, CD2Cl2, δ): 1.54 (d, 9H, JHP = 3 1C, CHarom.(B)), 129.2 (d, 1C, JCP = 2.4 Hz, CHarom.(A)), 129.4 16.8 Hz, tBu), 1.68 (d, 9H, JHP = 15.5 Hz, tBu), 2.75 (s, 3H, 2 – ̲– (d, 1C, JCP = 2.2 Hz, CHarom.(B)), 131.6 (s br., 1C, CHarom.(B)), CH3), 3.82 (d br., 1H, JHP = 12.3 Hz, P C(H) B), 7.46 (d, 1H, 3 3 134.7 (d, 1C, JCP = 2.2 Hz, CHarom.(A)), 135.1 (d, 1C, JCP = 2.9 JHH = 8.0 Hz, Hm-py), 8.12 (pseudo-t, 1H, JHH = 8.0 Hz, Hp-py), 3 31 1 Hz, CHarom.(A)), 136.1 (s br., 1C, CHarom.(B)), 143.0 (d, 1C, JCP = 8.32 (d, 1H, JHH = 8.1 Hz, Hm-py). P{H} NMR (121 MHz, This article is licensed under a δ 11 1 δ 1.6 Hz, CHarom.(A)), 143.9 (s br., 1C, CHarom.(B)), 157.9 (d, 1C, CD2Cl2, ): 31.1 (br.). B{H} NMR (96 MHz, CD2Cl2, ): 6.4. 13 1 JCP = 7.8 Hz, Cquat.(A)), 159.0 (d, 1C, JCP = 7.2 Hz, Cquat.(B)), C{H} NMR (75 MHz, CD2Cl2, δ): 18.1 (s, 1C, CH3), 29.3 (d, 2 2 161.3 (d, 1C, JCP = 2.5 Hz, Cquat.(B)), 164.4 (d, 1C, JCP = 3.7 Hz, 3C, JCP = 1.5 Hz, CH3tBu), 30.3 (s, 3C, JCP = 2.5 Hz, CH3tBu), 1 Open Access Article. Published on 09 June 2016. Downloaded 1/31/2020 3:03:39 AM. – – ̲ – – Cquat.(A)), the aromatic ipso-carbon connected to boron is not 32.9 36.1 (br., 1C, P C(H) B), 37.5 (d, 1C, JCP = 20.8 Hz, P 1 observed for A or B. CtBu), 38.5 (d, 1C, JCP = 15.2 Hz, P–CtBu), 123.8 (s, 1C, CHpy),

Complex 4. A solution of hydrochloric acid in diethylether 126.1 (s, 1C, CHpy), 144.7 (s, 1C, JCP = 1.2 Hz, CHpy), 153.6 (s, μ − (1 M, 86 L, 1.1 eq.) was added dropwise to a suspension of 1C, Cquat.), 159.0 (s br., 1C, Cquat.). HRMS (CSI, 35 °C): exact + anti-3·GaCl3 (42 mg, 78.4 μmol) in dichloromethane (2 mL) at mass (monoisotopic) calcd for [C15H25BCl2NP − (GaCl3)+H],

−78 °C and the resulting suspension was allowed to warm up 332.1276; found 332.1301. Anal. Calcd For C15H25BCl5GaNP; to room temperature overnight to give a colorless solution. The C, 35.46; H, 4.96; N, 2.76. Found: C, 35.56; H, 4.86; N, solution was filtered via cannula, the reaction flask was 2.67. M. p.: decomposition above 177 °C. washed with dichloromethane (1 mL) and the organic layers Complex 5·B(Cl)(Ph). Dichlorophenylborane (49.8 μL, were combined. The dichloromethane solution was layered 0.38 mmol, 1 eq.) in toluene (0.4 mL) was added dropwise at with pentane (8 mL), aﬀording colorless crystals of 4 with a room temperature to a solution of 2 (155 mg, 0.38 mmol) in yield of 89% at room temperature after one day. Crystals suit- toluene (3 mL) under stirring, leading to a colorless solution. able for X-ray diﬀraction analysis were obtained by layering a Analysis of the crude mixture by 1H NMR showed the for- dichloromethane solution of 4 with pentane at room tempera- mation of a mixture of diastereoisomers in a 1.9/1 ratio. After 1 3 ture. H NMR (300 MHz, CD2Cl2, δ): 1.14 (d, 9H, JHP = 15.3 removal of the volatiles under reduced pressure, the residue 3 Hz, tBu), 1.49 (d, 9H, JHP = 14.3 Hz, tBu), 2.59 (s, 3H, CH3), was dissolved in dichloromethane (4 mL) and filtered in order 3.85–4.08 (m, 2H, CH2), 6.29 (d, 1H, JHH = 7.4 Hz, Harom.), 7.19 to have a limpid solution. Layering of this solution with

(t, 1H, JHH = 7.4 Hz, Harom.), 7.37 (t br., 1H, JHH = 7.5 Hz, pentane (14 mL) aﬀorded colorless crystals of 5·B(Cl)(Ph) in

Harom.), 7.52 (t, 1H, JHH = 7.5 Hz, Harom.), 7.61 (d, 1H, JHH = 7.8 one day at room temperature with a yield of 51%. The mixture Hz, Harom.), 8.05 (m, 2H, Harom.), 8.30 (t, 1H, JHH = 7.8 Hz, of diastereoisomers was fully characterized by NMR spec- 31 1 11 1 Harom.). P{H} NMR (121 MHz, CD2Cl2, δ): 21.4 (br.). B{H} troscopy and the relative configuration of each isomer was δ 13 1 NMR (96 MHz, CD2Cl2, ): 5.9 (br.). C{H} NMR (75 MHz, attributed based on 2D NOESY NMR spectroscopy (in the case

Paper Dalton Transactions

of syn-5·BClPh, correlations are found between the B–C(H)̲– CH3), 29.4 (s, 3C, CH3tBu), 30.0 (s, 3C, CH3tBu), 35.2 (br., 1C, B– 1 – 1 PPh2 proton and the protons of the phenyl ring due to their C), 37.4 (d, 1C, JCP = 27.0 Hz, P CtBu), 38.0 (d, 1C, JCP = 21.1 spatial proximity, no correlation is observed with the anti Hz, P–CtBu), 124.9 (s, 1C, CHm-py), 125.7 (s, 1C, CHm-py), 144.3 1 isomer). For NMR: A = syn-5·B(Cl)(Ph);B=anti-5·B(Cl)(Ph). H (s, 1C, CHp-py), 153.0 (s, 1C, Co-py), 159.7 (s br., 1C, Co-py). Anal. δ 3 NMR (400 MHz, CD2Cl2, ): 0.95 (d, 9H, JHP = 16.4 Hz, tBu(B)), Calcd For C15H25B2Cl5NP; C, 40.10; H, 5.61; N, 3.12. Found: C, 3 3 1.44 (d, 9H, JHP = 15.4 Hz, tBu(A)), 1.61 (d, 9H, JHP = 17.9 Hz, 40.13; H, 5.63; N, 3.13. 3 tBu(A)), 1.61 (d, 9H, JHP = 15.0 Hz, tBu(B)), 2.30 (s, 3H, 2 – X-ray crystallography CH3(A)), 2.48 (s, 3H, CH3(B)), 3.74 (d, 1H, JHP = 15.2 Hz, P C 2 (H)̲–B (B)), 3.77 (d, 1H, JHP = 12.5 Hz, P–C(H)̲–B (A)), 7.23–7.42 X-ray intensities were measured on a Bruker D8 Quest Eco 3 (m, 5 HPh (B) and 5 HPh (A)and 1 Hm-py (A)), 7.49 (d, 1H, JHH = diﬀractometer equipped with a Triumph monochromator (λ = 3 8.0 Hz, Hm-py (B)), 8.10 (pseudo-t, 1H, JHH = 8.0 Hz, Hp-py (A)), 0.71073 Å) and a CMOS Photon 50 detector at a temperature of 3 3 8.16 (pseudo-t, 1H, JHH = 8.0 Hz, Hp-py (B)), 8.34(d, 1H, JHH = 150(2) K. Intensity data were integrated with the Bruker APEX2 3 31 1 20 8.1 Hz, Hm-py (B)), 8.38(d, 1H, JHH = 8.1 Hz, Hm-py (B)). P{H} software. Absorption correction and scaling was performed δ 11 1 21 NMR (121 MHz, CD2Cl2, ): 32.6 (br.). B{H} NMR (96 MHz, with SADABS. The structures were solved with the program 13 1 20 CD2Cl2, δ): 7.4. C{H} NMR (75 MHz, CD2Cl2, δ): 18.0 (s, 1C, SHELXL. Least-squares refinement was performed with 22 2 CH3(A)), 18.4 (s, 1C, CH3(B)), 29.0 (s, 3C, CH3tBu(B)), 29.2 (s, SHELXL-2013 against F of all reflections. Non-hydrogen 2 3C, CH3tBu(A)), 29.5 (s, 3C, CH3tBu(B)), 30.3 (d, 3C, JCP = 2.1 atoms were refined with anisotropic displacement parameters. 1 Hz, CH3tBu(A)), 32.8 (br., C–B(A) + C–B(B)), 37.1 (d, 1C, JCP = The H atoms were placed at calculated positions using the 1 22.7 Hz, P–CtBu(B)), 37.3 (d, 1C, JCP = 21.8 Hz, P–CtBu(A)), 37.6 instructions AFIX 13, AFIX 43 or AFIX 137 with isotropic dis- 1 – 1 – (d, 1C, JCP = 16.8 Hz, P CtBu(B)), 38.5 (d, 1C, JCP = 15.9 Hz, P placement parameters having values 1.2 or 1.5 times Ueq of the CtBu(A)), 123.7 (s, 1C, CHarom.(B)), 123.9 (s, 1C, CHarom.(A)), attached C atoms. CCDC 1455266–1455269 contain the sup-

125.4 (s, 1C, CHarom.(B)), 125.6 (s, 1C, CHarom.(A)), 127.9–128.6 plementary crystallographic data for this paper.

Creative Commons Attribution-NonCommercial 3.0 Unported Licence. (m, 3CHarom.(A) + 4CHarom.(B)), 128.7 (s, 1C, CHarom.(B)), 131.7 Details for 2. C20H25Cl2GaNP, Fw = 451.00, colorless, 0.327 × (s, 2C, CHarom.(A)), 143.6 (s, 1C, CHarom.(A)), 143.9 (s, 1C, 0.210 × 0.152 mm, monoclinic, P21/c (no: 14), a = 9.049(3), b = 3 CHarom.(B)), 153.6 (s, 1C, Cquat.(A)), 154.1 (s, 1C, Cquat.(B)), 9.165(3), c = 22.163(9) Å, β = 91.028(8)°, V = 1837.9(20) Å , Z = −3 μ −1 160.7 (s, 1C, Cquat.(A)), 161.1 (br., 1C, Cquat.(B)), the aromatic 4, Dx = 1.643 g cm , = 1.893 mm . 39 709 reflections were −1 ipso-carbon connected to boron is not observed for A or measured up to a resolution of (sin θ/λ)max = 0.65 Å . 7005

B. HRMS (CSI, −35 °C): exact mass (monoisotopic) calcd for reflections were unique (Rint = 0.0634), of which 5482 were − + σ [C21H29B1Cl1N1P1 (GaCl3)+H], 374.1980; found 374.2062. observed [I >2(I)]. 188 Parameters were refined with 0 Anal. Calcd For C21H30BCl4GaNP; C, 45.88; H, 5.50; N, 2.55. restraints. R1/wR2 [I >2σ(I)]: 0.0329/0.0687. R1/wR2 [all refl.]: Found: C, 45.61; H, 5.46; N, 2.50. 0.0517/0.0752. S = 1.008. Residual electron density between This article is licensed under a anti syn − −3 Isomerization of 5·BCl2 to -3·GaCl3 and -3·GaCl3. A 0.760 and 0.667 e Å . CCDC 1455266. colorless solution of 5·B(Cl)(Ph) (33.3 mg, 60.6 μmol) in Details for anti-3·GaCl3. C21H30BCl4GaNP, Fw = 549.76, color-

CD2Cl2 (0.4 ml) was heated to 100 °C in an NMR tube for 10 h, less, 0.478 × 0.201 × 0.199 mm, monoclinic, P21/c (no: 14), a = 1 Open Access Article. Published on 09 June 2016. Downloaded 1/31/2020 3:03:39 AM. leading to a yellow solution. Monitoring of the reaction by H 10.152(10), b = 16.382(9), c = 15.393(12) Å, β = 93.68(3)°, V = 3 −3 −1 NMR spectroscopy (internal standard = toluene 5 μL) showed 2555.(5) Å , Z =4,Dx = 1.467 g cm , μ = 1.609 mm . 29 499

the formation of a mixture of diastereoisomers 3·GaCl3 anti, reflections were measured up to a resolution of (sin θ/λ)max = −1 56%; syn, 38%) and traces of decomposition product 4 (3%). 0.84 Å . 4370 reflections were unique (Rint = 0.0384), of which The latter probably results from the addition of HCl (as traces 3954 were observed [I >2σ(I)]. 269 Parameters were refined

in the solvent) across the C–Ga bond of 3·GaCl3. with 252 restraints. R1/wR2 [I >2σ(I)]: 0.0240/0.0563. R1/wR2 Complex 6. To a solution of 1 (535.0 mg, 1.59 mmol) in di- [all refl.]: 0.0288/0.0591. S = 1.091. Residual electron density −3 ethylether (20 mL) was added BCl3 (1 M in solution in toluene; between −0.382 and 0.431 e Å . CCDC 1455267.

3.18 mL, 3.18 mmol, 2 eq.) at room temperature under stirring, Details for 4. C21H31BCl4GaNP, Fw = 550.77, colorless, 0.479 resulting in a colorless solution. After removal of the volatiles × 0.452 × 0.240 mm, triclinic, Pˉ1 (no: 1), a = 9.7845(7), b = under reduced pressure, the residue was dissolved in dichloro- 11.8465(9), c = 12.0322(9) Å, α = 83.458(3), β = 83.640(3), γ = 3 −3 methane, filtered and layered with pentane to give the 77.501(3)°, V = 1347.41(17) Å , Z =2,Dx = 1.358 g cm , μ = − expected compound 6 as colorless crystals with a yield of 48%. 1.486 mm 1. 70 054 reflections were measured up to a resolu- −1 Single crystals suitable for X-ray diﬀraction analysis were tion of (sin θ/λ)max = 0.64 Å . 10 873 reflections were unique 1 obtained using the same conditions. H NMR (300 MHz, (Rint = 0.0501), of which 8259 were observed [I >2σ(I)]. 278 δ 3 3 σ CD2Cl2, ): 1.59 (d, 9H, JHP = 14.9 Hz, tBu), 1.68 (d, 9H, JHP = Parameters were refined with 0 restraints. R1/wR2 [I >2(I)]: 2 13.4 Hz, tBu), 2.75 (s, 3H, CH3), 3.93 (d, 1H, JHP = 15.3 Hz, P– 0.377/0.746. R1/wR2 [all refl.]: 0.647/0.897. S = 1.076. Residual 3 −3 C(H)̲–B), 7.42 (d, 1H, JHH = 8.0 Hz, Hm-py), 8.06 (pseudo-t, 1H, electron density between −1.04 and 0.86 e Å . CCDC 1455269. 3 3 31 1 JHH = 8.1 Hz, Hp-py), 8.48 (d, 1H, JHH = 8.3 Hz, Hm-py). P{H} Details for 5·BCl2. C15H25BCl5GaNP, Fw = 508.11, colorless, 1 11 1 ˉ NMR (121 MHz, CD2Cl2, δ): 22.8 (q, JPB = 139.4 Hz). B{H} 0.312 × 0.268 × 0.108 mm, triclinic, P1 (no: 1), a = 8.483(6), b = 1 NMR (96 MHz, CD2Cl2, δ): 4.7 (d, JPB = 139.4 Hz, P–BCl̲ 3), 6.6 8.751(5), c = 16.791(7) Å, α = 87.39(2), β = 80.71(2), γ = 63.25(3)°, ̲ 13 1 δ 3 −3 μ −1 (br., BCl2). C{H} NMR (75 MHz, CD2Cl2, ): 18.0 (s, 1C, V = 1098.0(16) Å , Z =2,Dx = 1.560 g cm , = 1.963 mm .

Dalton Transactions Paper

33 460 reflections were measured up to a resolution 3 D. W. Stephan, J. Am. Chem. Soc., 2015, 137, 10018; θ λ −1 of (sin / )max = 0.74 Å . 5489 reflections were unique (Rint = D. W. Stephan and G. Erker, Angew. Chem., Int. Ed., 2015, 0.0589), of which 4453 were observed [I >2σ(I)]. 224 Parameters 54, 6400; D. W. Stephan, Acc. Chem. Res., 2015, 48, 306–316.

were refined with 252 restraints. R1/wR2 [I >2σ(I)]: 0.321/0.628. 4 C. Gunanathan and D. Milstein, Acc. Chem. Res., 2011, 44,

R1/wR2 [all refl.]: 0.491/0.685. S = 1.008. Residual electron 588; K. Junge, K. Schröder and M. Beller, Chem. Commun., − density between −0.469 and 0.503 e Å 3. CCDC 1455268. 2011, 47, 4849; J. I. van der Vlugt, Eur. J. Inorg. Chem., 2012,

Details for 6. C15H25B2Cl5NP, Fw = 449.20, colorless, 0.391 × 363; D. Gelman and S. Musa, ACS Catal., 2012, 2, 2456; 0.311 × 0.184 mm, triclinic, Pˉ1 (no: 1), a = 8.2835(19), b = W.-H. Wang, J. T. Muckerman, E. Fujita and Y. Himeda, 8.5491(18), c = 16.876(4) Å, α = 87.103(6), β = 81.076(7), γ = New J. Chem., 2013, 37, 1860; S. Kuwata and T. Ikariya, 3 −3 61.850(5)°, V = 1040.6(4) Å , Z =2,Dx = 1.434 g cm , μ = Chem. Commun., 2014, 50, 14290; R. H. Morris, Acc. Chem. − 0.773 mm 1. 34 045 reflections were measured up to a resolu- Res., 2015, 48, 1494. −1 tion of (sin θ/λ)max = 0.75 Å . 5215 reflections were unique 5 Recent reviews: J. I. van der Vlugt and J. N. H. Reek, Angew.

(Rint = 0.658), of which 4319 were observed [I >2σ(I)]. 227 Para- Chem., Int. Ed., 2009, 48, 8832; C. Gunanathan and σ meters were refined with 0 restraints. R1/wR2 [I >2 (I)]: 0.357/ D. Milstein, Chem. Rev., 2014, 114, 12024; 0.722. R1/wR2 [all refl.]: 0.502/0.774. S = 1.072. Residual elec- J. R. Khusnutdinova and D. Milstein, Angew. Chem., Int. − tron density between −0.32 and 0.58 e Å 3. CCDC 1481714. Ed., 2015, 54, 12236. See also: H. Li, B. Zheng and K.-W. Huang, Coord. Chem. Rev., 2015, 293–294, 116. Recent examples from our group: J. I. van der Vlugt, DFT calculations E. A. Pidko, D. Vogt, M. Lutz, A. L. Spek and A. Meetsma, 23 Calculations were carried out with the Gaussian09 software Inorg. Chem., 2008, 47, 4442; J. I. van der Vlugt, M. Lutz, 24 at the DFT level, using the hybrid functional B3PW91. Alumi- E. A. Pidko, D. Vogt and A. L. Spek, Dalton Trans., 2009, num, gallium, chlorine and phosphorus atoms were treated 1016; S. Y. de Boer, Y. Gloaguen, J. N. H. Reek, M. Lutz and

Creative Commons Attribution-NonCommercial 3.0 Unported Licence. with small-core pseudopotentials from the Stuttgart group, J. I. van der Vlugt, Dalton Trans., 2012, 41, 11276; S. Y. de 25 with additional polarization orbitals. Nitrogen, carbon, Boer, Y. Gloaguen, M. Lutz and J. I. van der Vlugt, Inorg. boron and H atoms have been treated with the all-electron Chim. Acta, 2012, 380, 336; L. S. Jongbloed, B. de Bruin, 6-31G** Pople basis set. The geometry optimizations were J. N. H. Reek, M. Lutz and J. I. van der Vlugt, Chem. – Eur. done without any symmetry constraints. Analytical calculations J., 2015, 21, 7297; L. S. Jongbloed, B. de Bruin, of the vibrational frequencies of the optimized geometries J. N. H. Reek, M. Lutz and J. I. van der Vlugt, Catal. Sci. were performed to confirm that the structures obtained were Technol., 2016, 6, 1320. See also: Y. Gloaguen, minimums, and also obtained the thermal corrections over C. Rebreyend, M. Lutz, P. Kumar, M. I. Huber, J. I. van der the energies. The Natural Bond Orbital analysis was done over Vlugt, S. Schneider and B. de Bruin, Angew. Chem., Int. Ed., This article is licensed under a the optimized structure, with the version of the NBO software 2014, 53, 6814; Z. Tang, S. Mandal, N. D. Paul, M. Lutz, 26 included in Gaussian09. P. Li, J. I. van der Vlugt and B. de Bruin, Org. Chem. Front., 2015, 2, 1561.

Open Access Article. Published on 09 June 2016. Downloaded 1/31/2020 3:03:39 AM. 6 Two known alternative binding modes are via phosphorus only or with P and N both binding to a different metal Acknowledgements center. For an example, see: J. I. van der Vlugt, E. A. Pidko, R. C. Bauer, Y. Gloaguen, M. K. Rong and M. Lutz, Chem. – This research is funded by the European Research Council Eur. J., 2011, 17, 3850. through ERC Starting Grant EuReCat 279097 to J. I. v. d. V. We 7 Transmetallation of P-only coordinated mononuclear Ag- thank Prof.’s Bas de Bruin and Joost Reek for general support species to e.g. Pd has been reported: J. I. van der Vlugt, and interest in our work and Ed Zuidinga for MS analysis. M. A. Siegler, M. Janssen, D. Vogt and A. L. Spek, Organo- metallics, 2009, 28, 7025. 8 L. A. Körte, R. Warner, V. Y. Vishnevskiy, B. Neumann, References H.-G. Stammler and N. W. Mitzel, Dalton Trans., 2015, 44, 9992; J. Zheng, Y.-J. Lin and H. Wang, Dalton Trans., 2016, 1 R. Kinjo, B. Donnadieu, M. A. Celik, G. Frenking and 45, 6088. G. Bertrand, Science, 2011, 333, 610; C. Fliedel, G. Schnee, 9 L.-C. Liang, M.-H. Huang and C.-H. Hung, Inorg. Chem., T. Avilés and S. Dragorne, Coord. Chem. Rev., 2014, 275, 63. 2004, 43, 2166; H. Naka, M. Uchiyama, Y. Matsumoto, 2 I. A. Cade and M. J. Ingleson, Chem. – Eur. J., 2014, 20, A. E. H. Wheatley, M. McPartlin, J. V. Morey and Y. Kondo, 12874; M. Devillard, R. Brousses, K. Miqueu, G. Bouhadir J. Am. Chem. Soc., 2007, 129, 1921. and D. Bourissou, Angew. Chem., Int. Ed., 2015, 54, 5722; 10 J. I. van der Vlugt, E. A. Pidko, D. Vogt, M. Lutz and J. M. Farrell, R. T. Posaratnanathan and D. W. Stephan, A. L. Spek, Inorg. Chem., 2009, 48, 7513; M. Montag, Chem. Sci., 2015, 6, 2010; Z. Yang, M. Zhong, X. Ma, J. Zhang and D. Milstein, J. Am. Chem. Soc., 2012, 134, K. Nijesh, S. De, P. Parameswaran and H. W. Roesky, J. Am. 10325; C. A. Huff, J. W. Kampf and M. S. Sanford, Organo- Chem. Soc., 2016, 138, 2548. metallics, 2012, 31, 4643; C. A. Huff, J. W. Kampf and

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